Throughout this application various publications are referred to in parentheses. Full citations for these references may be found at the end of the specification. The disclosures of these publications, and all patents, patent application publications and books referred to herein, are hereby incorporated by reference in their entirety into the subject application to more fully describe the art to which the subject invention pertains.
Despite the medical importance of coronary arteries, their embryonic origins and developmental mechanisms remain unclear. These arteries are the loci for coronary artery disease, the most widespread disease in western societies. Elucidating mechanisms of coronary artery formation may help recapitulate this developmental process for coronary artery regeneration.
Coronary arteries have 3 tissue layers: the inner layer of endothelium, the middle layer of smooth muscle cells, and the outer layer of fibroblasts. The endothelium is the first layer formed during coronary artery formation. Primitive coronary vessels (or coronary plexuses) consist of one endothelial cell layer. The plexuses then recruit smooth muscle cells and fibroblasts to assemble mature arteries. Endothelium is also the first site where coronary artery disease occurs in adults. Thus identifying the cellular origins of coronary endothelium is essential to elucidate mechanisms of coronary artery development or regeneration.
The heart is made of three major tissue layers: the endocardium, myocardium, and epicardium. The myocardium is the central layer, and the coronary vasculature forms within this layer during development. The epicardium is the outermost epithelial layer of the heart; it is derived from the proepicardium outside the heart (Komiyama et al., 1987; Viragh and Challice, 1981). Studies have shown that epicardial cells generate coronary vascular smooth muscle cells (Cai et al., 2008; Dettman et al., 1998; Mikawa and Fischman, 1992; Mikawa and Gourdie, 1996; Vrancken Peeters et al., 1999; Zhou et al., 2008). It is less clear whether proepicardial/epicardial cells make any significant contribution to coronary endothelial cells, although some coronary endothelial cells in avian species are derived from proepicardial cells (Mikawa et al., 1992; Perez-Pomares et al., 2002). Fate-mapping studies in mice have suggested the sinus venosus as a common origin of the endothelium of coronary arteries and veins (Red-Horse et al., 2010) while a subset of proepicardial cells also contribute to some coronary endothelial cells (Katz et al., 2012).
The endocardium is the internal epithelial layer of the heart. Endocardial cells are one of the earliest endothelial populations acquired in development, differentiating from multipotent progenitors in the cardiac field (Misfeldt et al., 2009; Sugi and Markwald, 1996; Yamashita et al., 2000; Yang et al., 2008). They form an endocardial tube by vasculogenesis and later become the endocardium of the heart (Drake and Fleming, 2000). Endothelial cells of coronary vessels arise later in development and form coronary vessels in the myocardium (Lavine and Ornitz, 2009; Luttun and Carmeliet, 2003; Majesky, 2004; Olivey and Svensson, 2010; Wada et al., 2003). Ventricular endocardial cells have been thought to be terminally differentiated without a significant role in coronary vessel formation. However, even in light of this knowledge, coronary artery regeneration technology is still in need of better understanding and techniques.
The present invention addresses this need by providing novel coronary artery regeneration methods and compositions.